The -4 refers to an engineering change
Denotes it as a "Victory" model, produced for WWII
Made @ 1974
No such model number. However, if you mean a 15-4, 50-450 USD.
If you mean Smith and Wesson, inside the frame near the crane if it has one. Model numbers did not come into use until @ 1957
Cartridge
manufacturing mark
Most likley an assembly number.
The fifth engineering change in the Model 10 line.
Model 91 is a model number for handcuffs. If you mean a Single Shot Model of 1891, the single shot pistol, 100-2000 depending on EXACTLY what you have and condition.
possibly the serial number....
If you mean a Model 52, 100-1000 USD or so
returned for repair is most likely